Despite many advances in the diagnosis and treatment of cardiovascular disease (CVD) over the past several decades, it remains the leading cause of death and disability in the US and is one of the fastest rising causes of morbidity and mortality globally. This highlights the importance of ascertainment of contemporary and robust data on CVD epidemiology, use and consequences of CVD therapies, and longitudinal outcomes. The HMO Research Network is a consortium of 15 not-for-profit health plans geographically distributed throughout the U.S. with integrated research divisions committed to public domain research that advances population health through its work among its >11 million health plan members. This community-based network provides a unique opportunity to fill key knowledge gaps related to CVD identified by the National Heart, Lung and Blood Institute in RFA-HL-07-011, "Cardiovascular Research Network (CVRN) in Community-Based Care." Therefore, the overall aims of our proposal are to: Aim 1. To establish a collaborative Cardiovascular Research Network (CVRN) among 14 member plans of the HMO Research Network to create a unique national resource that leverages the network's cardiovascular expertise, diverse community-based study populations, and rich electronic data systems. Aim 2. To leverage the HMO Research Network CVRN to conduct three core research projects that demonstrate the network's capability to provide insights into trends in cardiovascular disease, risk factors, and outcomes;identification of prognostic factors;and evaluation and improvement of management and associated clinical outcomes of cardiovascular conditions. The core research projects will target hypertension control, quality of care and outcomes of warfarin therapy for atrial fibrillation and venous thromboembolism, and the use and outcomes of implantable cardioverter defibrillators. Aim 3. To implement an effective model structure within the HMO Research Network CVRN to rapidly respond to emerging cardiovascular research questions and to facilitate productive external collaborations that maximize the value and productivity of the CVRN. Section A: Overall Program Review